JP4031064B2 - Repeater device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a repeater device, and more particularly to a repeat device used for a LAN using a twisted pair line among LANs based on the IEEE 802.3 standard.
[0002]
[Prior art]
One standard for a local area network (LAN) is the IEEE 802.3 standard by the 802 committee of the Institute of Electrical and Electronics Engineers. The IEEE 802.3 standard defines several types of LANs. Among them, a star type such as 1Base5 or 10Base-T adopting a CSMA / CD (carrier sense multiple access / collision detection) method as an access method. There is a LAN. As shown in FIG. 5, a LAN is configured by connecting a plurality of terminal devices and repeater devices such as HUBs and concentrators using twisted pair wires. 5A shows a STAR LAN with 1Base5 (transmission speed of 1 Mbps), and FIG. 5B shows a LAN called Ethernet with 10Base-T (transmission speed of 1 Mbps).
[0003]
[Problems to be solved by the invention]
In 1Base5 and 10Base-T according to the IEEE 802.3 standard, 1 Mbps and 10 Mbps are defined as data transmission rates, respectively. That is, these LANs have different transmission rates. For this reason, there is a problem that a repeater device designed to comply with each standard (corresponding to each transmission speed) cannot be connected to a terminal device of a different standard. That is, there is a problem that the conventional repeater device is not versatile.
[0004]
At present, 100Base-T with a transmission rate of 100 Mbps is being standardized in the 802 committee of the Institute of Electrical and Electronics Engineers of Japan, and it seems that LANs based on this standard will become the mainstream. When doing so, we must consider coexistence with the existing LAN. Therefore, considering the connection between an existing LAN and a new standard LAN, in addition to the existing LAN repeater device and the new standard LAN repeater device, a router or a bridge connected between these repeater devices, etc. There is a problem that a device having a speed conversion function is required and the network configuration is complicated.
[0005]
As described above, the conventional repeater device is designed and manufactured in accordance with each standard, and has a problem of being versatile. In addition, in order to connect devices of different standards to the repeater device, a device having a speed conversion function is required, which causes a problem that the network configuration becomes complicated.
[0006]
It is an object of the present invention to provide a repeater device that can connect a terminal device that complies with any standard, thereby simplifying the network configuration.
[0007]
[Means for Solving the Problems]
According to the present invention, a preamble detection means for detecting a preamble of an input data signal, and a transmission speed of the data signal by receiving the preamble detected by the preamble detection means and counting the number of bits for a predetermined time. A transmission rate measuring unit for measuring the transmission rate, and a clock signal corresponding to the transmission rate measured by the transmission rate measuring unit, and the preamble is not input to the transmission rate measuring unit within the predetermined time. There is obtained a repeater device comprising clock generation means for switching the frequency of an operation clock supplied to the preamble detection means and the transmission rate measurement means from a first frequency to a second frequency lower than the first frequency .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a repeater apparatus having an embodiment of the present invention. Here, the repeater apparatus usually has a plurality of sets of input / output ports, but all the circuit configurations connected to the respective ports are the same. Therefore, here, for simplicity of explanation, a repeater having one set of input / output ports is used. The apparatus will be described.
[0009]
This repeater device includes a pair of input ports 11, a receiver circuit 12, a preamble detection circuit 13, an input signal detection circuit 14, two crystal oscillators 15a and 15b, a changeover switch 16, a clock controller 17, a waveform shaping circuit 18, and a driver circuit. 19 and an output port 20.
[0010]
A twisted pair line (not shown) from the terminal device is connected to the input port 11 and a data signal transmitted through the twisted pair line is input. The data signal input to the input port is converted into a data signal of a predetermined format in the receiver circuit 12 and input to the preamble detection circuit 13.
[0011]
A sampling clock from the crystal oscillator 15a is input to the preamble detection circuit 13 via the changeover switch 16, and the input data signal is sampled using this sampling clock.
[0012]
Here, the data signal and sampling clock input to the preamble detection circuit 13 will be described. The IEEE 802.3 standard LAN adopts the CSMA / CD method as an access method, and the frame structure (packet structure) of the data signal is as shown in FIG. That is, preamble, SFD (start frame delimiter), transmission destination address (DESTINATION ADDRESS), transmission source address (SOURCE ADDRESS), packet length (LENGTH), data, PAD (dummy data), and FCS (FRAME CHECK SEQUENCE; Frame check sequence). Among these, the preamble is a synchronization pattern provided for synchronization on the receiving side, and its length is defined as 7 octets, that is, 56 bits.
[0013]
On the other hand, the frequency of the sampling clock from the crystal oscillator 15a is set to a frequency that is at least four times that of the fastest data signal among the data signals input to the input port 11. For example, assuming that 1Base5 and 10Base-T of the IEEE 802.3 standard and 100Base-T that will be standardized are input, 100 Mbps of 100Base-T is set to 400 MHz or higher because 100 Mbps is the fastest. .
[0014]
For example, if the data signal (100 Mbps) having the preamble shown in FIG. 3A is input to the preamble detection circuit 13, the frequency higher than the transmission speed as shown in FIG. This is because sampling results as shown in FIG. 3C can be obtained by sampling using the (800 MHz) sampling clock. Of course, when the input data signal is lower than that shown in FIG. 3A, the same signal as the input data signal can be obtained by performing sampling in the same manner.
[0015]
Thus, the preamble detection circuit 13 can detect the preamble by specifying the input data signal by sampling regardless of the transmission speed of the input data signal. The preamble detection circuit 13 outputs a data signal specifying the preamble to the input / output measurement circuit 14.
[0016]
Similar to the preamble detection circuit 13, the input signal measurement circuit 14 receives a sampling clock from the crystal oscillator 15a. The sampling clock is used to measure a predetermined time and count how many bits of the preamble portion are input within the predetermined time. Thereby, the transmission rate of the input data signal can be obtained. If the 1-bit pulse width is measured, the transmission rate can be obtained more accurately. The measurement accuracy can be increased by repeating these operations to obtain the average value.
[0017]
If no bit is input to the input signal measurement circuit 14 within a predetermined time, the selector 16 is instructed to select the crystal oscillator 15b. The crystal oscillator 15b has a frequency lower than that of the crystal oscillator 15a and is set to, for example, a period that is four times or more of 1 Mbps of 1Base5, and thus can cope with a data signal having a low transmission rate.
[0018]
The input signal measurement circuit 14 detects the rising edge of the preamble portion, outputs this rising signal (signal shown in FIG. 3D) to the clock controller 17 and the changeover switch 16, and obtains the pulse interval by each controller. Thus, the transmission rate may be obtained.
[0019]
Thus, the transmission speed measured by the input signal measuring circuit 14 is notified to the clock controller 17. The clock controller 17 divides the clock signal from the crystal oscillator 15 a or the crystal oscillator 15 b input via the changeover switch 16 to generate a transmission clock, and outputs it to the waveform shaping circuit 18.
[0020]
The waveform shaping circuit 18 performs waveform shaping by synchronizing the data signal (same as the signal shown in FIG. 3C) input via the input signal measurement circuit 14 with the transmission clock from the clock controller 17, and the driver circuit 19 output. The driver circuit 19 amplifies the signal from the waveform shaping circuit 18 with a predetermined amplification factor and supplies it to the output port 20.
[0021]
As described above, the repeater device having this embodiment measures the transmission rate of the input data signal, generates the measured clock, and performs waveform shaping, so that a plurality of different transmission rates can be obtained. It can also handle data signals. That is, if the repeater device has a plurality of input / output ports, terminal devices with different standards can be accommodated in one network as shown in FIG.
[0022]
The present invention can be applied not only to a repeater device but also to other signal processing devices.
[0023]
【The invention's effect】
According to the present invention, by using the preamble of the input data signal, the transmission speed of the data signal is measured, and the clock corresponding to the transmission speed is generated, so that the standards for different transmission speeds can be achieved. It is possible to provide a repeater device that can be connected to an adapted terminal device. Thereby, even if LANs of different standards coexist, the network configuration can be simplified.
[Brief description of the drawings]
FIG. 1 is a block diagram of a repeater device having an embodiment of the present invention.
FIG. 2 is a diagram illustrating a frame configuration used in the CSMA / CD system.
FIG. 3 shows input / output signals of each part of one repeater device, where (a) is a data signal input to the preamble detection circuit 13, (b) is a sampling clock, and (c) is input from the preamble detection circuit 13. The output signal to the signal measurement circuit 14 and (d) show the waveform of the output signal from the input signal measurement circuit 14 to the clock controller 17.
FIG. 4 is a diagram showing a configuration of a LAN using the repeater device of the present invention.
5A and 5B are diagrams showing a configuration of a conventional LAN, in which FIG. 5A shows a star LAN and FIG. 5B shows an Ethernet.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Input port 12 Receiver circuit 13 Preamble detection circuit 14 Input signal measurement circuit 15a, 15b Crystal oscillator 16 Changeover switch 17 Clock controller 18 Waveform shaping circuit 19 Driver circuit 20 Output port

Claims (3)

Preamble detection means for detecting a preamble of an input data signal, and transmission speed measurement for measuring the transmission speed of the data signal by receiving the preamble detected by the preamble detection means and counting the number of bits for a predetermined time And a clock signal corresponding to the transmission rate measured by the transmission rate measurement unit, and when the preamble is not input to the transmission rate measurement unit within the predetermined time, the preamble detection unit and the A repeater apparatus comprising: a clock generation unit that switches a frequency of an operation clock supplied to the transmission rate measurement unit from a first frequency to a second frequency lower than the first frequency . The clock generation means includes an oscillator that generates a sampling clock having a frequency that is at least four times the highest transmission speed of the input data signal, and a clock control means that generates the clock signal from the sampling clock. and, the repeater apparatus according to claim 1, characterized in that the sampling clock to be supplied as an operation clock of said first frequency to said preamble detection means and the transmission rate measuring unit. It said clock signal repeater apparatus according to claim 1 or 2, characterized in that it has a waveform shaping means for shaping a waveform and retiming of the data signal with.

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